U.S. patent application number 13/644833 was filed with the patent office on 2014-04-10 for wireless communications system including single channel retransmission and related methods.
This patent application is currently assigned to Harris Corporation. The applicant listed for this patent is HARRIS CORPORATION. Invention is credited to James P. Lill, Nelson H. Powell, III, William S. Rogers.
Application Number | 20140098718 13/644833 |
Document ID | / |
Family ID | 50432598 |
Filed Date | 2014-04-10 |
United States Patent
Application |
20140098718 |
Kind Code |
A1 |
Powell, III; Nelson H. ; et
al. |
April 10, 2014 |
WIRELESS COMMUNICATIONS SYSTEM INCLUDING SINGLE CHANNEL
RETRANSMISSION AND RELATED METHODS
Abstract
A wireless communications system may include wireless
communications devices configured to communicate with one another
on a given channel via a time division based communications
protocol. A communication initiation wireless communications device
configured to transmit data in an initiator time slot of the given
channel. A repeater wireless communications device configured to
receive the transmitted data from the communications initiation
wireless communications device in the initiator time slot and
retransmit the data in a repeater time slot of the given channel. A
receiver wireless communications device configured to determine a
respective quality metric for data from each of the initiator time
slot and the repeater time slot, and use data from the initiator
time slot or the repeater time slot based upon the respective
quality metrics thereof.
Inventors: |
Powell, III; Nelson H.;
(Penfield, NY) ; Lill; James P.; (Rochester,
NY) ; Rogers; William S.; (Webster, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HARRIS CORPORATION |
Melboume |
FL |
US |
|
|
Assignee: |
Harris Corporation
Melboume
FL
|
Family ID: |
50432598 |
Appl. No.: |
13/644833 |
Filed: |
October 4, 2012 |
Current U.S.
Class: |
370/279 ;
370/315 |
Current CPC
Class: |
H04W 72/0446 20130101;
H04W 88/04 20130101; H04W 72/085 20130101 |
Class at
Publication: |
370/279 ;
370/315 |
International
Class: |
H04W 88/04 20090101
H04W088/04; H04W 72/04 20090101 H04W072/04 |
Claims
1. A wireless communications system comprising: a plurality of
wireless communications devices configured to communicate with one
another on a given channel via a time division based communications
protocol; said plurality of wireless communications devices
comprising a communication initiation wireless communications
device and configured to transmit data in an initiator time slot of
the given channel, a repeater wireless communications device
configured to receive the transmitted data from said communications
initiation wireless communications device in the initiator time
slot and retransmit the data in a repeater time slot of the given
channel, and a receiver wireless communications device and
configured to determine a respective quality metric for data from
each of the initiator time slot and the repeater time slot, and use
data from the initiator time slot or the repeater time slot based
upon the respective quality metrics thereof.
2. The wireless communications system of claim 1, wherein said
receiver wireless communications device is configured to use data
from the repeater time slot based upon the initiator time slot
having no data.
3. The wireless communications system of claim 1, wherein said
receiver wireless communications device is configured to use data
from the initiator time slot based upon the repeater time slot
having no data.
4. The wireless communications system of claim 1, wherein said
receiver wireless communications device is configured to retransmit
the used data in a further repeater slot on the given channel to a
downstream wireless communications device.
5. The wireless communications system of claim 1, wherein the
respective quality metric comprises at least one of a bit error
rate (BER) and a signal strength.
6. The wireless communications system of claim 1, wherein the time
division based communications protocol comprises time division
duplexing (TDD).
7. The wireless communications system of claim 1, wherein time
division based communications protocol comprises time division
multiple access (TDMA).
8. The wireless communications system of claim 1, wherein time
division based communications protocol comprises a time division
frequency hopping protocol.
9. The wireless communications system of claim 1, wherein said
initiator wireless communications device is configured to disregard
data received in the repeater time slot while transmitting in the
initiator time slot.
10. A wireless communications system comprising: a plurality of
wireless communications devices configured to communicate with one
another on a given frequency via a time division based
communications protocol; said plurality of wireless communications
devices comprising a communication initiation wireless
communications device configured to transmit data in an initiator
time slot of the given frequency, a repeater wireless
communications device configured to receive the transmitted data
from said communications initiation wireless communications device
in the initiator time slot and retransmit the data in a repeater
time slot of the given frequency, and a receiver wireless
communications device and configured to determine a respective
quality metric for data from each of the initiator time slot and
the repeater time slot, use data from the initiator time slot or
the repeater time slot based upon the respective quality metrics
thereof, and use data from the repeater time slot based upon the
initiator time slot having no data.
11. The wireless communications system of claim 10, wherein said
receiver wireless communications device is configured to retransmit
the used data in a further repeater slot on the given frequency to
a downstream wireless communications device.
12. The wireless communications system of claim 10, wherein the
respective quality metric comprises at least one of a bit error
rate (BER) and a signal strength.
13. The wireless communications system of claim 10, wherein the
time division based communications protocol comprises time division
duplexing (TDD).
14. The wireless communications system of claim 10, wherein time
division based communications protocol comprises time division
multiple access (TDMA).
15. A method of wireless communication in a wireless communications
system comprising a plurality of wireless communications devices
configured to communicate with one another on a given channel via a
time division based communications protocol, the method comprising:
transmitting from a communication initiation wireless
communications device from among the plurality of wireless
communications devices data in an initiator time slot of the given
channel; receiving at a repeater wireless communications device
from among the plurality of wireless communications devices the
transmitted data from the communications initiation wireless
communications device in the initiator time slot; retransmitting
from the repeater wireless communications device the data in a
repeater time slot of the given channel; determining at a receiver
wireless communications device from among the plurality of wireless
communications devices a respective quality metric for data from
each of the initiator time slot and the repeater time slot; and
using, at the receiver wireless communications device, data from
the initiator time slot or the repeater time slot based upon the
respective quality metrics thereof.
16. The method of claim 15, further comprising using, at the
receiver wireless communications device, data from the repeater
time slot based upon the initiator time slot having no data.
17. The method of claim 15, further comprising using, at the
receiver wireless communications device, data from the initiator
time slot based upon the repeater time slot having no data.
18. The method of claim 15, further comprising retransmitting from
the receiver wireless communications device the used data in a
further repeater slot on the given channel to a downstream wireless
communications device.
19. The method of claim 15, wherein determining respective quality
metric comprises determining at least one of a bit error rate (BER)
and a signal strength.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of communications
and, more particularly, to wireless communications and related
methods.
BACKGROUND OF THE INVENTION
[0002] It may be desirable to retransmit data, for example, voice
data, in a wireless communications system. One approach to
retransmitting data may include implementing a retransmission site
or system using two wireless communications devices. A two device
retransmission system typically operates using multiple frequencies
and multiple antennas, for example, one for receiving data and
another for retransmitting the data, to avoid a collision.
Co-location interference mitigation techniques are typically used
in such a two device approach. In some implementations, the two
wireless communications devices may be configured to operate in a
back-to-back configuration.
[0003] One example, of a two device retransmission system is the
Single Channel Ground and Airborne Radio System (SINCGARS).
SINCGARS uses multiple wireless communications devices at a given
retransmission site and operates using multiple frequencies. One
frequency is for a transmitting network. One frequency is for a
repeater network. One radio receives data while one radio
transmits. This may be accomplished via a back-to-back cable
connection.
[0004] Another approach to retransmitting data may include
implementing a retransmission site or system using a single
wireless communications device. Similar to the two device approach
described above, a single device retransmission system operates
using multiple frequencies and multiple antennas. Operator
coordination is also typically required for retransmission
sequences. For example, operator coordination may be desired when
the retransmission is directly performed. Furthermore, in a single
device system retransmission of streaming data, such as, for
example, streaming audio, may not be possible, as retransmission
are performed in bursts rather than a synchronous data stream.
[0005] U.S. Pat. No. 4,513,412 to Cox discloses a time division
adaptive retransmission technique for portable radio telephones.
More particularly, Cox discloses a portable transceiver and a
remote terminal station each using at least two antennas with
different polarization transmission capabilities for an adaptive
retransmission technique. The terminal station transmits the same
preamble signal in at least two time slots of a frame period of a
time division sequence using the antenna receiving the strongest
signal from the transceiver in the immediately prior frame period
followed by a binary message signal using the same antenna. The
transceiver receives each of the preamble transmissions from the
terminal station via a separate one of differently oriented
antennas and determines which antenna received the strongest
signal. The message signal from the terminal station is then
received via the antenna of the transceiver having received the
strongest signal and also sends its response message signal on that
antenna during a separate time slot of a frame period.
[0006] U.S. Pat. No. 7,031,658 to Dibernardo discloses a single
radio retransmission system using a half duplex radio. More
particularly, Dibernardo discloses a transmitting terminal using
only a transmit segment of a frame, and a receiving terminal using
only the receive segment of each frame. A retransmission terminal
receives data in its receive segment and transmits the data,
buffered, in its transmit segment.
SUMMARY OF THE INVENTION
[0007] In view of the foregoing background, it is therefore an
object of the present invention to provide a single channel
wireless retransmission system.
[0008] This and other objects, features, and advantages in
accordance with the present invention are provided by a wireless
communications system that includes a plurality of wireless
communications devices configured to communicate with one another
on a given channel via a time division based communications
protocol. The plurality of wireless communications devices includes
a communication initiation wireless communications device
configured to transmit data in an initiator time slot of the given
channel. The wireless communications system also includes a
repeater wireless communications device configured to receive the
transmitted data from the communications initiation wireless
communications device in the initiator time slot and retransmit the
data in a repeater time slot of the given channel. A receiver
wireless communications device is configured to determine a
respective quality metric for data from each of the initiator time
slot and the repeater time slot, and use data from the initiator
time slot or the repeater time slot based upon the respective
quality metrics thereof. Accordingly, the wireless communications
system advantageously retransmits data on a single channel. More
particularly, a single wireless communications device, i.e., the
repeater wireless communications device, receives and retransmits
the data on a given channel or frequency thereby reducing system
complexity compared to multiple devices and/or multiple frequency
management.
[0009] A method aspect is directed to a method of wireless
communication in a wireless communications system that includes a
plurality of wireless communications devices configured to
communicate with one another on a given channel via a time division
based communications protocol. The method includes transmitting
from a communications initiation wireless communications device
from among the plurality of wireless communications devices, data
in an initiator time slot of the given channel.
[0010] The method also includes receiving at a repeater wireless
communications device from among the plurality of wireless
communications devices, the transmitted data from the
communications initiation wireless communications device in the
initiator time slot. The method further includes retransmitting
from the repeater wireless communications device the data in a
repeater time slot of the given channel.
[0011] The method further includes determining, at a receiver
wireless communications device from among the plurality of wireless
communications devices, a respective quality metric for data from
each of the initiator time slot and the repeater time slot. The
method also includes using, at the receiver wireless communications
device, data from the initiator time slot or the repeater time slot
based upon the respective quality metrics thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic diagram of a wireless communications
system in accordance with the present invention.
[0013] FIG. 2 is a schematic block diagram of mobile wireless
communications devices of the wireless communications system of
FIG. 1.
[0014] FIG. 3 is a timing slot structure for an example,
implementation of the wireless communications devices of FIG.
2.
[0015] FIG. 4 is a schematic diagram of an example implementation
of the wireless communications system of FIG. 1.
[0016] FIG. 5 is another schematic diagram of an example
implementation of the wireless communications system of FIG.
[0017] FIG. 6 is a schematic diagram of a wireless communications
system in accordance with another embodiment of the present
invention.
[0018] FIG. 7 is a schematic diagram of receiver wireless
communications devices of the system of FIG. 6.
[0019] FIG. 8 is a timing slot structure for use with the wireless
communications system of FIGS. 6 and 7.
[0020] FIG. 9 is a more detailed schematic diagram of a timing slot
structure for use with a wireless communications system according
to the present invention.
[0021] FIG. 10 is a more detailed schematic diagram of the
initiator time slots of FIG. 9.
[0022] FIGS. 11a-11c are schematic diagrams of a wireless
communications system according to another embodiment of the
present invention.
[0023] FIG. 12 is a flow chart of a method of wireless
communication in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout, and prime notation is used to indicate similar
elements in alternative embodiments.
[0025] Referring initially to FIGS. 1-3, a wireless communications
system 20 includes mobile wireless communications devices 21a-21c.
The wireless communications devices 21a-21c communicate with one
another on a given channel via a time division based communications
protocol. More particularly, the wireless communications devices
21a-21c communicate with each other on a given frequency via time
division duplexing (TDD) in some embodiments. In other embodiments,
the wireless communications devices 21a-21c may communicate with
each other via time division multiple access (TDMA), or a frequency
hopping time division multiple access (FH-TDMA) protocol. In the
case of the wireless communications devices 21a-21c communicating
via FH-TDMA, the given channel corresponds to the frequencies of
communication and these frequencies change over time.
[0026] In a single hop configuration, the wireless communications
devices 21a-21c communicate data with each other on one of two time
slots of a plurality of time slots 33, that is an initiator time
slot I.sub.1, I.sub.2 and a repeater time R.sub.1, R.sub.2 slot.
The data may be voice data, for example. In other embodiments, the
data may be another type of data, such as, for example, packet
based data. The time slots each have a fixed width. The slot width
is dictated by bandwidth available versus bandwidth desired. In
other words, the slot width is based upon a desired voice rate. The
net bit rate should be greater than the vocoder bit rate, for
example, by at least a factor of two. The voice slots are evenly
spaced apart maintaining a constant time/slot distance. There are
also delay/propagation time slots D to account for turnaround time
between time slots, and more particularly, between the initiator
time slot and the repeater time slots.
[0027] By way of example, the given channel may be a high frequency
(HF) channel, and the wireless communications devices 21a-21c may
be HF wireless communications devices communicating with each other
at an HF frequency. When the given channel is an HF frequency, for
example, the voice/data time slot width may be 220 ms with an 80 ms
propagation time. This is based upon an assumed 2400 bps modem, 600
bps voice codec, and a 21 byte overhead. The 80 ms is for
propagation delay due to around the world bounce. The 21 byte
overhead typically accounts for the MAC address, the security
parameters, the primitive message type, etc. Therefore, when the
channel is HF, 600 ms of voice may be transmitted in a 220 ms slot,
which provides enough time for a repeater to receive the message
and turn around a retransmission in a second 220 ms slot, for
example. It should be noted that this timing is based on a short
path retransmission, and delays would be recalculated for a long
path retransmission.
[0028] A first wireless communications device 21a defines a
communication initiation wireless communications device. The
communication initiation wireless communications device 21a
includes a housing 28a, and processor 22a and a memory 23a coupled
thereto and carried by the housing. The communication initiation
wireless communications device 21a also includes an audio output
transducer 24a and an audio input transducer 25a, both carried by
the housing 28a. The communication initiation wireless
communications device 21a may include additional input devices. A
wireless transceiver 26a is also coupled to the processor 22a, and
a respective antenna 27a is coupled to the wireless transceiver.
The wireless transceiver 26a cooperates with the processor 22a to
perform at least one of data and voice communications function.
[0029] The processor 22a is configured to transmit data in the
initiator time slot I.sub.1 over the given channel, i.e., at the
given frequency. More particularly, the communication initiation
wireless communications device 21a is the source of the digital
audio stream, for example, via the audio input transducer 25a. The
processor 22a may ignore any digital voice data that may be in the
repeater time slot while transmitting data in the initiator time
slot I.sub.1. For example, the given channel may be internally
monitored to ascertain conditions for determining whether to adjust
output power.
[0030] A second wireless communications device 21b defines a
repeater wireless communications device. The repeater wireless
communications device 21b includes a housing 28b, and a processor
22b and a memory 23b coupled thereto and carried by the housing. A
wireless transceiver 26b is also coupled to the processor 22b, and
a respective antenna 27b is coupled to the wireless transceiver.
The wireless transceiver 26b cooperates with the processor 22b to
perform at least one data and/or voice communications function.
[0031] The processor 22b is configured to receive the transmitted
data from the communications initiation wireless communications
device 21a in the initiator time slot I.sub.1. The processor 22b is
configured to retransmit the digital voice data in the repeater
time slot R.sub.1 of the given channel, i.e. at the given
frequency. The processor 22b retransmits the data in the repeater
time slot R.sub.1 based upon the receipt of the digital voice data
in the initiator time slot I.sub.1. Prior to retransmission of the
digital voice data, the processor 22b adds header information
indicative of the source of the retransmission. In other words, the
processor 22b adds header information so that a downstream
receiving wireless communications device is aware of the source of
the received digital voice data.
[0032] The repeater wireless communications device 21b also
includes an audio output transducer 24b and an audio input
transducer 25b carried by the housing 28b and coupled to the
processor 22b. The processor 22b plays the digital voice data via
the audio output transducer 24b between the two delay/propagation
slots D after the repeater time slot R.sub.1, but before the
initiator time slot I.sub.2 in the next sequence. Of course, in
embodiments where the data is not digital voice data, for example,
the repeater wireless communications device 21b may not include an
audio output transducer. Instead, the repeater wireless
communications device 21b may include a display, for example, or
other device for outputting the data.
[0033] A third wireless communications device 21c defines a
receiver wireless communications device. The receiver wireless
communications device 21c includes a housing 28c, and a processor
22c and a memory 23c coupled thereto carried by the housing. A
wireless transceiver 26c is also coupled to the processor 22c, and
a respective antenna 27c is coupled to the wireless transceiver.
The wireless transceiver 26c cooperates with the processor 22c to
perform at least one data of and voice communications function.
[0034] The processor 22c is configured to determine a respective
quality metric for the digital voice data from each of the
initiator time slot I.sub.1 and the repeater time slot R.sub.1. For
example, the quality metric may include a bit error rate of the
digital voice data in each of the initiator and repeater time slots
I.sub.1, R.sub.1. The quality metric may also include signal
strength data for the digital voice data in each of the initiator
and repeater time slots I.sub.1, R.sub.1.
[0035] Similar to the repeater receiver wireless communications
device 21b, the receiver wireless communications device 21c also
includes an audio output transducer 24c and an audio input
transducer 25c coupled to the processor 22c. The processor 22c
plays the digital voice data via the audio output transducer 24c
between delay/propagation slots D after the repeater time slot
R.sub.1, but before the initiator time slot I.sub.2 in the next
sequence. The digital voice data is played from the initiator time
slot I.sub.1 or the repeater time slot R.sub.1 based upon the
respective quality metrics thereof. Of course, in other embodiments
where the data is not necessarily digital voice data, the processor
22c uses data from the initiator time slot or the repeater time
slot R.sub.1 based upon the respective quality metrics thereof and
outputs the data accordingly.
[0036] Additionally, the processor 22c is also configured to play
back or use digital voice data from the repeater time slot R.sub.1
based upon the initiator time slot I.sub.1 having no data. Still
further, the processor 22c is configured to play back or use data
from the initiator time slot I.sub.1 based upon the repeater time
slot R.sub.1 having no data. For example, in the next transmission
sequence, the processor 22c may play back digital audio data with
the determined respective quality metrics being that there is no
digital voice data in either of the initiator time slot or the
repeater time slot I.sub.2, R.sub.2. It should be noted that when
the receiver wireless communications device 21c plays back the
digital voice data, the repeater wireless communications device may
also play back the digital voice data, i.e., they are synchronized.
The process (initiation, retransmission, and receiving) may be
repeated for the next time sequence based upon the next initiation
time slot I.sub.2 and the next repeater time slot R.sub.2, and also
for subsequent time sequences.
[0037] Referring now to FIG. 4, one advantageous implementation of
an example wireless communications system 20 may be in an HF
system. Illustratively, the communications initiation wireless
communications device 21a, the repeater wireless communications
device 21b, and the receiver wireless communications device 21c are
geographically spaced apart at ground level of the Earth. HF
signals may propagate using skywave propagation based upon the
Earth's ionosphere, line of sight, or groundwave propagation, for
example. The communications initiation wireless communications
device 21a transmits buffered audio in the initiator time slot. A
single frame of audio is transmitted by the communications
initiation wireless communications device 21a. The repeater
wireless communications device 21b receives the frame of audio via
line of sight 45 and waits 80 ms (assuming a short path
retransmission) before retransmitting the same data packet or
digital voice data. The communications initiation wireless
communications device 21a waits 160 ms plus the time for
transmission before transmitting a second digital audio packet. The
receiver wireless communications device 21c receives the frame of
audio from both the initiations wireless communications device 21a
via ionospheric bounce 44, and via line of sight 46 from the
repeater wireless communications device 21b. The receiver wireless
communications device 21c determines which reception is best based
upon the quality metric, i.e., the initiator time slot or the
repeater time slot. The receiver wireless communications device 21c
plays back the digital audio from the initiator time slot or the
repeater time slot based upon the respective quality metrics
thereof.
[0038] Referring now to FIG. 5, another advantageous implementation
of an example wireless communications system 20 may be in an HF
system. The communications initiation wireless communications
device 21a transmits digital voice data in the initiator time slot,
but near vertical incidence skywave (NVIS) 47 fails because of too
steep of an angle. Line of sight transmission 48 also fails because
of a blockage, for example, a mountain. Illustratively, the
repeater wireless communications device 21b, which is beyond the
line of sight from the communications initiation wireless
communications device 21a, receives the transmitted digital voice
data via skywave 51. The repeater wireless communications device
21b retransmits the digital voice data in the repeater time slot,
and because of the ionospheric bounce 52, the retransmitted digital
voice data is received at the receiver wireless communications
device 21c. Of course, there is a delay, for example, for
propagation, between receipt of the digital voice data and the
retransmission of the digital voice data. This implementation may
be particularly advantageous for 3G automatic link establishment
(ALE) for broadcasting of data, for example.
[0039] Referring now to FIGS. 6-8, in another embodiment, the
receiver wireless communications device 21c' may also function as a
repeater wireless communications device. More particularly, when
there are three time slots, the number of hops may be theoretically
infinite.
[0040] The processor 22a' of the communications initiation wireless
communications device 21a' originates and transmits digital voice
data in the initiator time slot I.sub.1 at time T.sub.ORIG of the
timing slot structure 34'. It is noted that T.sub.# refers to time
by the number of hops, I.sub.# refers to an initiator time slot,
and R.sub.# refers to a repeater time slot. The communications
initiation wireless communications device 21a' has a range 31a'
associated therewith. The repeater wireless communications device
21b', which has a range 31b' associated therewith, retransmits the
digital voice data in the first repeater time slot R.sub.1 at
T.sub.1. The processor 22c' of the receiver wireless communications
device 21c' analyzes the header information of the digital voice
data received in either or both of the initiator and repeater time
slots I.sub.1, R.sub.1. The receiver wireless communications device
21c' has a range 31c' associated therewith. Based upon the header
information, the processor 22c' may select to operate as a repeater
wireless communications device and retransmit the played back
digital voice data, i.e., based upon the respective quality
metrics, in a second repeater time slot R.sub.2. The receiver
wireless communications device, when operating as a repeater
wireless communications device, retransmits the digital voice data
in a second repeater time slot R.sub.2 at T.sub.2.
[0041] The communications initiation wireless communications device
21a' can then again transmit or originate digital voice data in the
initiator time slot I.sub.2 at T.sub.ORIG of the next sequence. The
DV data is repeated at T.sub.1 and T.sub.2 as described above in
the respective first and second repeater time slots R.sub.21,
R.sub.22 of the next sequence. Additional retransmissions are
denoted by T.sub.3, T.sub.4, and T.sub.5 respectively by wireless
communications devices 21d', 21e', 21f', having respective ranges
31d', 31e', 31f', where T.sub.# is the number of hops from the
communications initiation wireless communications device 21a'. Each
of the wireless communications devices 21d' and 21e' operates
similar to the receiver wireless communications device 21c'
described above in that they operate also as a repeater wireless
communications device. Wireless communications device 21f' operates
as a receiver wireless communications device, but may also operate
as a repeater wireless communications device to provide service to
downstream devices.
[0042] Illustratively the digital voice may be repeated at T.sub.3
in the initiator time slot since the mobile device 21d'
corresponding to T.sub.3 on the next sequence is out of range 31a'
of the communications initiation wireless communications device
21a' (T.sub.ORIG). In other words, retransmissions occupy the same
three slots as the original and first two repeaters.
Advantageously, the effect and occurrence of collisions are reduced
due to the time and distance.
[0043] Referring now additionally to FIG. 9, timing of
transmissions or retransmissions is illustrated in the diagram 35.
In a fixed frequency channel, for example, in TDD, the timing is
fixed. The timing includes a time for transmission T.sub.T, a time
for propagation T.sub.P, and a time of delay T.sub.D. A TDD
implementation may allow for asynchronous startup and reception,
for example. More particularly, the repeater wireless
communications device 21b may correlate on a preamble of the
digital voice data (packet), which is described in further detail
below. Alternatively, startup may occur with receipt of any digital
voice data packet or audio stream due to packetization, for
example.
[0044] Illustratively, the communications initiation wireless
communications device 21a transmits in the initiator time slot
I.sub.1 of, for example, 80 ms. Prior to the repeater wireless
communications device 21b retransmitting the digital voice data in
the repeater time slot R.sub.1, the repeater wireless
communications device waits a time for propagation T.sub.P, a time
of delay T.sub.D, and another time for propagation T.sub.P. After
another set of a time for propagation T.sub.p, a time of delay
T.sub.D, and another time for propagation T.sub.P, the
communications initiation wireless communications device 21a again
transmits in the initiator time slot I.sub.2. In other words, the
communications initiation wireless communications device 21a waits
a total of 4 T.sub.P and 2 T.sub.D before transmitting again. The
communications initiation wireless communications device 21a and
the repeater wireless communications device 21b alternate
transmitting. Audio play back may occur anytime after the
transmitted data from the repeater wireless communications device
21b is receiver and/or processed, or should have been received
and/or processed. Audio play back may also be buffered, i.e.
delayed, further before play back.
[0045] Referring now additionally to FIG. 10, an example voice
frame, for example, transmitted in the initiator time slot I.sub.1
is illustrated. The digital voice data or frame in an initiator
time slot I.sub.1 includes a source media access control (MAC)
address slot 53 having a size of 8 bits. The source MAC address
slot 53 includes a fixed pre-defined MAC address that identifies
the source of the transmission, i.e., the communications initiation
wireless communications device 21a. The source MAC address has the
same value even from the repeater wireless communications device
21b.
[0046] The initiator time slot I.sub.1 also includes a transmission
type slot 54 having a size of 4 bits. The transmission type slot 54
identifies the type of transmission as either an original
transmission (0x00) or a retransmission from the first repeater
wireless communications device (0x01) 21b.
[0047] The initiator time slot I.sub.1 also includes a digital
voice block 55 following the transmission type slot and having a
size of 4 bits. The digital voice block 55 is used for infinite hop
layout, for example, up to 2.sup.N hops. The digital voice block 55
allows for differentiation between sequences received out of order,
for example.
[0048] Following the digital voice block 55, a repeat count slot 56
having a size of 4 bits. If there is more than one repeater
wireless communications device, each wireless communications device
uses the hop count to identify its distance from the original
source, i.e. the initiator wireless communications device. Data
within the repeat count slot 56 indicates a number of hops from the
source of the digital voice data, i.e., the number of hops from the
communications initiation wireless communications device 21a. This
advantageously allows a wireless communications device to determine
it should retransmit the received data. An optional cryptographic
block 57 of 16 bits follows the repeat count slot 55 and may be
used for block cipher, for example.
[0049] A digital voice (DV) frame 58 follows the cryptographic
block 57 and has a size of 1080 bits. Packaged digital voice, or
data, is packaged in the DV frame 58. For example, the digital
voice frame 58 may include 20 frames of coded audio at 2400 bits
per second. The data rate is less than the channel rate, and the
packaged digital voice may not be decoded prior to retransmission
for a repeater wireless communications device. The DV frame 58 may
include a bit error rate (BER) pattern for receiver diversity if
direct signal-to-noise ratio detection is not possible. The voice
frame layout described above with respect to the initiator time
slot I.sub.1 is also applicable to subsequent initiator time slots,
for example, I.sub.2.
[0050] Referring now additionally to FIGS. 11a-11c, an example
wireless communication system illustrating the concept of receiver
diversity is shown. Referring particularly to FIG. 11a, the
communication initiation wireless communications device 21a''
transmits the DV data in the initiator time slot. The repeater
wireless communications device 21b'' receives the transmitted data
from the communications initiation wireless communications device
21a''. Wireless communications device 21b'' retransmits the DV data
in the repeater time slot.
[0051] Since wireless communications device 21d'' is within ranges
31a'', 31b'' of wireless communications devices 21a'', 21b'',
wireless communications device 21d'', i.e., a receiver wireless
communications device, receives both the transmitted data from the
communications initiation wireless communications device 21a'' and
the retransmitted data from the repeater wireless communications
device 21b'', and may determine, as described above, which data
from the initiator time slot or the repeater time slot to use.
Wireless communications devices 21c'' and 21f'' receive the
retransmitted data from the repeater wireless communications device
21b'' since it is within range 31b'', but does not receive the
original transmitted DV data since they are out of range 31a'' of
the communications initiation wireless communications device 21a''.
Wireless communications device 21e'' receives transmitted data from
the communications initiation wireless communications device 21a'',
and operates as a repeater wireless communications device.
[0052] Referring now more particularly to FIG. 11b, the mobile
device 21f'' moves to within the range 31a'' of the communications
initiation wireless communications device 21a'' as illustrated.
Wireless communications device 21f'' receives both the transmitted
data from the communications initiation wireless communications
device 21a'' and the repeater wireless communications device 21b''
since it is now within respective ranges 31a'', 31b''. The wireless
device 21f'', defining a receiver wireless communications device,
plays back the DV data based upon the respective quality metrics as
described above. It should be noted that the wireless
communications device 21f'' may initially play back DV data based
upon the data received by the communications initiation wireless
communications device 21a'', but, for example, because of changes
in the quality metrics, may switch to play back DV data from the
repeater wireless communications device 21b''. This change may be
relatively seamless to a user, for example.
[0053] Referring more particularly to FIG. 11c, the mobile device
21f'' moves outside the range 31b'' of the repeater wireless
communications device 21b'', but remains within the range 31a'' of
the communications initiation wireless communications device 21a''.
The wireless device 21f'' has also moved within the range of
wireless communications device 21e''. Wireless communications
device 21e'' defines a repeater wireless communications device so
that wireless communications device 21f'' receives DV data from
both the communications initiation wireless communications device
21a'' and the wireless device 21e''. The wireless device 21f''
plays back the DV data based upon the respective quality metrics as
described above. If, for example, mobile device 21f'' were out of
range of wireless device 21e'', the wireless device 21f'' would
receive DV data only from the communications initiation wireless
communications device 21a'' and play back the DV audio using the
data within the initiator time slot. It should be noted that any of
the wireless communications devices may operate in any role as a
repeater, initiator, or receiver.
[0054] Referring now to the flowchart 110 in FIG. 12, beginning at
Block 112, a method aspect is directed to a method of wireless
communication in a wireless communications system 20 including a
plurality of wireless communications devices 21a, 21b, 21c
configured to communicate with one another on a given channel via a
time division based communications protocol. The method includes at
Block 114, transmitting from a first wireless communications device
21a defining a communication initiation wireless communications
device, data in an initiator time slot over the given channel.
[0055] At Block 116, the method includes receiving at a repeater
wireless communications device 21b from among the plurality of
wireless communications devices, the transmitted data from the
communications initiation wireless communications device in the
initiator time slot. The repeater wireless communications device
21b retransmits the data in a repeater time slot of the given
channel (Block 118).
[0056] At Block 120, the method includes determining, at a receiver
wireless communications device 21c from among the plurality of
wireless communications devices, if the initiator and repeater time
slots have data. If both the initiator and repeater time slots have
data, a respective quality metric for data from each of the
initiator time slot and the repeater time slot is determined (Block
122). The respective quality metrics are compared at Block 124 to
find out which of the initiator time slot and the repeater time
slot has higher quality data. If the initiator time slot has higher
quality data, based upon the respective quality metric, the
receiver wireless communications device 21c uses the data from the
initiator time slot (Block 126). Alternatively, if the repeater
time slot has higher quality data, based upon the respective
quality metric, the receiver wireless communications device 21c
uses the data from the repeater time slot (Block 128).
[0057] If it was determined at Block 120 that one of the initiator
or repeater time slots have data, the receiver wireless
communications device 21c uses data from the time slot having data
(Block 130). The method ends at Block 132.
[0058] While in the embodiments described, functions have been
described by way of the wireless devices performing the functions,
it should noted that the respective processors of each wireless
communications device cooperate with the respective memory to
perform the corresponding functions. Moreover, while the data has
been described with respect to digital voice data, it should be
noted that the principles of the embodiments described herein may
be applicable to other types of data communicated using any time
based protocol. Many modifications and other embodiments of the
invention will come to the mind of one skilled in the art having
the benefit of the teachings presented in the foregoing
descriptions and the associated drawings. Therefore, it is
understood that the invention is not to be limited to the specific
embodiments disclosed, and that modifications and embodiments are
intended to be included within the scope of the appended
claims.
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